This proposed research project is the PI's first R21 submission. The project aims at articulating the relationship between sleep problems (SPs) and substance use/ problems in adolescence and young adulthood. Research in adults indicates that insomnia predicts subsequent onset of substance abuse. Several cross-sectional studies suggest that SPs are positively related to substance use in adolescence. However, only a few prospective studies exist on the relationship between insomnia and alcohol use earlier in life. So far the data indicate SPs are related to onset of substance use in boys but not in girls. In response to PA-06-238, the current proposal seeks funding to support secondary data analysis from the Michigan Longitudinal Study (MLS). The project has four specific aims. First, we examine whether earlier sleep problems prospectively predict onset of substance use in adolescence and young adulthood. Second, we test whether earlier sleep problems prospectively predict escalation in substance use and abuse once onset begins. Third, we examine potential mediators of the relationship between sleep problems and substance use. Three mediators will be examined - behavioral problems, peer group choices, and neurophysiological arousal. Fourth, we evaluate how perceived stress may moderate the relationships between sleep problems and substance use. We are especially interested in possible gender differences related to these four aims. The Michigan Longitudinal Study is an ongoing family study currently in its 19th year. The study recruited a community sample of alcoholic and control families. Male and female offspring of these families have been interviewed from preschool age (3-5 years old) to young adulthood (18-21 years old) at 3-year intervals. Participants were also interviewed at yearly intervals from ages 11 to 17. Information regarding SPs and all other variables was collected at each wave. Data on substance use were gathered from the participants beginning at age 9. This project has the potential to document another, more physiologically proximal mechanism related to those affect and behavioral indicators already known to be central in the emergence of substance use and problems. This is the first work of its kind, and if successful, would lead to more elaborated studies on the effects of sleep problems on substance use and affect regulation.